Background: Glaucoma is a group of diseases of different etiologies with progressive optic nerve degeneration as well as loss of retinal ganglion cells (RGCs) with a subsequent visual impairment. It remains a primary cause of irreversible blindness. So, early diagnosis and treatment of glaucoma has been demonstrated to reduce the rate of disease progression and improve cases's quality of life. Spectral domain-optical coherence tomography (SD-OCT) technologies play an essential role in glaucoma management. Objective: To determine and compare the use of thickness of macular ganglion cell complex (GCC) and peripapillary retinal nerve fiber layer (ppRNFL) using OCT in diagnosis of glaucoma. Patients and methods: This was a comparative study carried out on 40 eyes. The eyes were classified into two groups: Group A that represented: 10 normal eyes as a control of the study, and Group B that included 30 eyes with glaucoma classified as regards disease severity into: 10 eyes with early glaucoma, 10 eyes with moderate glaucoma, and 10 eyes with severe glaucoma as regards Hodapp, Parrish, and Anderson (H-P-A) classification. Comprehensive ophthalmic examination, white-on-white perimetry and SD-OCT were done for entire cases. The OCT was done using 3D-OCT (Topcon) 2000 to evaluate the following: RNFL parameters average (total, superior and inferior) thickness and GCC parameters average (total, superior and inferior) thickness. Results: There was a positive statistically significant association of high probability between the two groups regarding RNFL thickness, GCC thickness, intraocular pressure (IOP), and vertical and linear cup-to-disc ratio (P<0.001). Conclusion: Early diagnosis of glaucoma and initiation of therapy was of high significance, as additional vision loss can be stopped or slowed down. RNFL and GCC measurement with SD-OCT could provide essential data for detection and assessment of glaucoma. GCC thickness and RNFL thickness demonstrated comparable diagnostic value as markers of early, moderate, and severe glaucoma. There was a strong positive association between the RNFL thickness and the GCC thickness in the glaucomatous cases.